If you choose to keep it as a sporter and re-mount a scope, you'll have to comb the auction sites for a vintage weaver (or equivalent) side mount. Brownells would be a good place to look for a current weaver produced side mount.
When I was 16, I had a sporterized 30-40
Krag
. It was drilled for a weaver side mount that could also be mounted (with drilling) on an SMLE MkIII. The mount base had a round profile to match the curved receivers of the 98 Krag and the SMLE MkIII. As your No4 has a flat side, it should be relatively easy to locate a flat-side mount. A few pics from auctions:
Attachment 105080Attachment 105081
Just remember these two pics were randomly pulled, and are not necessarily the correct ones for the No4. There are several. That might be half the fun in trying to locate the correct one.
Whatever path you choose, have fun, enjoy your rifle, and welcome to the forum.