Converting a .22 Enfield to magazine feed

[Gaz]

I have a No.4 that's been sleeved down to .22 and fitted with some Canadian No.7 parts. I've been wondering for a while about trying to get it to feed from a magazine nested inside the 303 mag shell, as a long term "what if" type project. The obvious candidate is the BSA Sportsman Five magazine but these seem exceedingly rare. What other short/slim magazines might work?

[dromia]

There is the original Parker Hiscock magazines, but they seem to be going for silly money if what I was offered for this one recently is anything to go by.

They work very well but aren't squaddie proof and they were originally made for the SMLE but should fit inside a No4 magazine body.