I tried one of the CDNN Korean 20s, worked fine in my WASR with a good lockup, no wobble. Didn't seat quite as smoothly as the surplus Romanians mine came with but could probably be fixed with a file. Someone else (maybe Centerfire) has them for the same price. CDNN charges flat $10 shipping last time I ordered mine. Like all Asian/Korean AK mags the steel is thin but functions fine. Biggest complaint of the Asian mags seems to be the feed lips separating and causing misfeeds but my 20 is better made than previous Asian 30s I've seen.
The Hungarian Tankers are the best and the most expensive for $27 a pop. But every one I've bought has been in Like New condition and seem to work in every rifle I can find. If I bought more 20s I'd probably just spring for these.
The Tapco 20s work fine in my WASR as well after filing the sides down a bit, I think they can be had for about $9 as well. The springs in my Tapco 20s are much shorter than either the Tankers or the Korean 20s, hasn't caused a problem yet but it's the only criticism I have for the Tapcos.