Hi @Starfield and welcome to the forum!
I very much hope you’re planning on attaching a sizeable anchor to the retrieval cord because if it starts moving up your colon the retrieval cord will be heading straight up too.
Having said that, if you are determined, then this Juno egg might be a good option as you can tie (securely!!) something wide to the retrieval cord’s loop and the silicone bullet housing is very secure. I have this egg (for vaginal use), it is too small for me to really enjoy so doesn’t get used much but the vibrations are good, the connection to the remote is excellent and on the noise activated mode the battery lasts a really long time. Also, both the vibe and the remote are rechargeable simultaneously from the same USB cable so no pesky replacing of remote batteries. My review of the egg is here if you want to read it.