I haven't been here often lately so I don't know if these have been recently suggested, but I have a couple of suggestions for simple rectal injectors for small amounts of glycerin &c. For me, just about 2cc (2ml) in enough to help me get a strong urge when I need just a bit of help, and it works almost immediately, though not very deeply like a bisacodyl suppository. My DIY injectors are 10ml, though, but most plastic plunger syringes will do. So, a few years ago I described what is still my own favorite DIY squirter. It was made from the nozzle end (only) from a Fleet brand disposable enema, unique in having a little ring groove molded into the interior of the nozzle just as the wide rubbery part thins into the long nozzle. That seems to still be true: it was on the enema I bought two weeks ago! (Push the nozzle proper down through the hard plastic screw-cap to release just the nozzle.) Then I cut the wide end from a 10 ml plastic oral syringe CAP so it made a shoulder washer, which fit perfectly into the ring in the nozzle. The nozzle-and-washer fit tightly onto the short (Luer-slip) syringe tip, by pressing tightly. I ended up with a tubular plastic syringe which sported a Fleet enema nozzle end: that was dandy for many uses; it was easily cleaned just by drawing in water and squirting it out to rinse. HOWEVER, at this time I cannot readily locate a plastic syringe sold with a cap with a "brim" of just the right size to lock into the ring groove.
So now I have found an even simpler solution. Purchase a plastic tubular syringe usually sold as oral or pet-feeding syringe, such as the Amazon BOF42HXZBV 10ml size, ten for $5.59; also purchase a catheter tip BOB9H49BXCD in size 16 French. These are about 6 inches long, and cost $9.99 for 30. These will not connect together, but just cut off 2 or 3 inches or so of the tube, which has a nice and comfy rounded end with holes in the side of the tube - whatever you need to get past the sphincters. The 16F size tube can be simply pressed firmly onto the short plastic syringe tip and it will stay there securely until you pull it off! These can be easily cleaned by rinsing with water in the same way, or, at only $0.33 each, they can be replaced when they get grungy. (These syringes are sold with caps, but the brims are not wide enough to lock into a Fleet nozzle.)
The finger-hold tabs on the syringes are handy, but if you cut or grind them mostly off the whole gizmo will easily fit into many toothbrush cases! And one more tip: when you put these away do NOT seat the plunger completely because some rubber plunger ends stick when completely closed; I leave the plunger out maybe half an inch.
And bye again to all! - jillie