I've always had great luck with any good-condition Adventure Line magazine, whether the original USGI 20rd mag or the later 30rd magazines. They've always been completely reliable for me over the years, even with the dreaded "black"-follower in the 30rd mags. I especially like Adventure Line 20rd magazines, excellent and very reliable magazines. The finish is especially durable compared to what the other USGI manufactures' seem to use at the time.
To the OP, Brand New D&H magazines can be found for around $8.00 per magazine from either PSA or Widener's these days. Good luck.