DIY option:
Commercial bore guides are basically just expensive funnels. So....I've made a few bore guides out of carbon fiber golf club shafts. Shafts are tapered so all one needs to do is cut the shaft where it will fit in the breech end of the chamber with a little overlap. Usually, the taper fit will prevent solvent from leaking back into the receiver, especially if the rifle is tilted muzzle down. The overall length has to be long enough to clear the back end of the receiver plus a bit so that it can be removed with fingers and short enough so that the cleaning rod tip extends past the muzzle. On some DIY bore guides, I have had to drill out the hole at the narrow end of the golf shaft so that a patched jag can pass through as well as a patched loop can pass through without wringing solvent from a wet patch.
I can buy used golf clubs from the local GoodWill for a buck.
