When it comes to molds for making suppositories I use some large plastic syringes which we use at my workplace for dispensing glue, sealants and grease.
These have a nozzle at the top end which I guess is for fitting a needle, but they don't come with a needle of course.
The ones I use are BD Plastipak brand, total length is 5 inches and the inside diameter is 1 inch with a capacity of 60 mL.
With the plunger pulled all the way back the internal length is 4½ inches, so I can make suppositories which are 4½ x 1 inch.
I cut the top end off the syringe to open the end of it and then pull the plunger all the way back to make an excellent mold. I put in a little cooking oil and roll it around to cover all the inside surface. The allows the suppository to slide out easily and the plunger is used to push it out as you probably guessed.
I have a length of timber 2 inch x 12 inch with holes bored in it to allow the plunger to pass through and the syringes have "ears" at the plunger end which provide something for the syringes to stand upright. I can line up 6 syringes on this piece of timber which I just prop up on a brick at each end. I didn't bother making legs for it because I was in a rush to make suppositories! They are made using Copha (solidified coconut oil) which is melted, and then while it's still warm (i.e.- not yet beginning to solidify) I add honey – about 3 parts honey to 1 part Copha. They will solidify at room temperature, but cooling in the fridge will be faster and make them harder, and the honey is its own preservative so the suppositories will keep for quite some time. They are a useful treatment for hemorrhoids (anal or rectal), especially if you can get some medicinal (Manuka) honey which has the better antibacterial properties. But the benefit of honey is that it has a slight irritation effect in the rectum and, after holding it as long as I can, it causes a quite explosive discharge and a thorough purging of the bowels.
After insertion I push them as deep as possible using a dildo, which is really the plastic water tank from a squirt gun (water pistol), and its advantage as a dildo is that it is smooth polypropylene, 5 inch x 1½ inch with a rounded tip and shaped like a large penis. So it is very often used to give myself some anal pleasure if the real thing is not available, either by hand or fitted onto my f*cking machine. This device is mounted on a low table at bum height and I assume the doggy position and back up to it for a lengthy period of anal ramming. Before doing so I generally use one of my unmodified syringes to inject about a quarter cup of cooking oil into my rectum and this leaks out during the ramming process producing a rather messy (which is fun!) and very slippery form of lubrication. Sometimes I also use a cucumber by hand, and of course these can be selected at the grocery in any length and diameter desired!
After the suppository has done it's job then I have an enema to flush myself, and this is sometimes done using an empty sauce bottle filled with warm water (those plastic ones with the twist nozzle on it), or I use a length of plastic hose attached to the washbasin tap in the bathroom which has a length of plastic pipe (electrical conduit) at the delivery end. This is bent at 90 degrees and it has a rubber tip on it. So I can sit on the toilet, put it between my legs and insert the tip into my anus and enjoy a refreshing warm water enema. Generally this is done by relaxing my anus and allowing the water to freely flow out.
Afterwards, with empty bowels, I often have discharges of gas so I insert a 6 inch length of 1 inch diameter plastic hose which has a ball shaped collar on the end, formed from silicon sealant. This acts as an "exhaust pipe" and allows the fart to escape without effort, and it also serves to stretch my anus as a form of exercise to keep it a little less tight for those times when I am with a man and I can be f*cked with less discomfort. I may have this hose inserted for several hours, or even all night.
So... the syringes I use make a very good suppository mold, but if you want something simple and easy to obtain then have a look at this silicone cylinder ice cube tray: http://www.ebay.com.au/itm/311402269168?_trksid=p2057872.m2749.l2649&ssPageName=STRK%3AMEBIDX%3AIT