i need to prevent the bike from wet sumping
How bad is it John - if it's not spewing oil out onto your garage floor when you start it then it's not doing anything out of the ordinary.
If you don't ride it as often as you would like (like me) that is no excuse to not start it at least once a week, every two or three days would be better, this will keep the sump empty, if it doesn't then you do indeed have a problem, a problem you should not have on a rebuilt engine, (although I do note you say rebuilt bike, maybe this does not include engine)
Anti wet sumping valves - a subject of divided opinions, I and my friends with BSA'a have used them with good good results, others don't trust them and go to great lengths to make them safe by fitting more things to go wrong ( Just a little dig guys don't take it personal like), do a search on the Forum John For wet sumping and be prepared for a long read.