A Shubb 5th string capo doesn't care which side it's on either.
I used to use Mr Happy's drawing board clip years ago, but they don't always fit properly (depends on the banjo), and they're a bit intrusive on the neck.
HO railroad spikes are very good - care needed when you insert them. These days I don't bother - Tunes in A and D can be played just by tuning the fifth string up to A. My fith strings been going up and down like a bride's nighty for years without breaking strings.
Cheers
Ray