after a lot of experimenting, i discovered the Tantus Ryder (i have it in purple), it comes in a medium size that is pretty comfortable. (well, as comfortable as wearing a foreign object in your backside can get i guess, lol) you have to keep in mind tho that everyone is different and what may be comfortable for me may not necessarily be comfortable for you. there are also some things to keep in mind when shopping for one. for instance, it tends to be easier for your body to adjust to a plug if it is small at the tip and more gradually widens toward the base...rather than being more wide or rounded out at the tip... length can also be an issue, the longer ones don't make for very comfy sitting and such when you are wearing them, lol! pending on the size and shape, if it is too small, you may discover that it wants to pop out of your bum on it's own as well. (imagine sneezing or coughing and your plug plopping out onto the floor, lmfao!) you will probably want to make sure it is at least big enough to stay in on its own. you may end up even purchasing a few before you find the one that is just right for you.
happy hunting!
Whisperz