Seems like some stamp collector has bought out all of Wojtec's supply of 5/8 SFK Wapienicas. He's listing 45 in stock on ebay for $16 a piece (about a $4 price hike since last time I checked Wojtec's listings). The upshot is that the shipping is down from $8 to $4, so as long as you aren't buying more than 2, you aren't paying much more.

Wojtec still sells the 9/16ths, and also some combination items (strops + hones + razors) with the 5/8 listed. I dunno if he'll list any new ones, but there are none being offered from him anymore currently.