Probably not what you're going to like to hear, but get with Big Jim and buy some more. With being that short of a need, I don't think any adapter would work. The threads would be too close.
If you could get the inserts out and shim it out with 1/4" of shaft material, reinsert the insert, then aluminum foot, you might be OK, but buying another half doz is easier and more true.
Or become a contributor and sell what you have to cover buying more/trading for more.
How long BOP are your current ones?