There are a variety of “larger” moulds that do resemble a commercially manufactured suppository / anal toy😲 for example :
• Large lead sinker moulds as in fishing weights work well, as does the smaller size Pyrex Glass lab test tubes. Aluminium cigar tubes (if available) & Blood specimen vials with sealing caps are another.
• Soaps can be reduced down to a slurry by boiling in water (after paring down with a potato peeler) add in a calibrated quantity of glycerine & food grade gelatine to re-solidify, stand upright in the fridge till it sets firm & then you're good to go . . . . .not that difficult
• Select (diameter) & cut a length of PVC tubing to the length you want, sand both ends to ensure that they are smooth around both the inner lip edge & outer cut edge so they're Jag free.
Then after washing & wiping dry, wipe the inside with a suitable lubricant followed by unravelling a condom to place inside the pre-lubed barrel . . . Allow the condom to pass right through so that the ‘teat’ end is left exposed by around an inch (25 mm) to an inch & a half, giving a nice smooth slightly bulbous shaped elongated head when finished. On the opposite end roll the condoms remaining rubber ring over the top & down the side . . .Fill with your choice of filler & place in the fridge upright to set. . . To remove from PVC pipe mould simply roll the collar end up & push it through to release.
NB : Where no bulbous head is wanted just retract the condom so that the ‘teat’ is barely visible.
Another Mould making technique can be easily achieved with that simpilest of stuff called Plaster Paris
Done properly by taking your time will deliver (lol) a professional looking product
Think outside the box !! . . . . or of it 😁