Mr Picky’s googling also seems to produce a pretty poor selection, and I cannot find any WW2 cards with Swastika backs; they all seem to be pre-WW2 uses of the decoration, like the “Nazi poker chips” found elsewhere which are nothing of the sort. One seller has the cheek to offer “Genuine 1912 Nazi swastika cards”, which I suppose serves the buyer right if they don’t know the Nazis weren’t around in 1912.
If you do produce a bespoke set, you might also care to note that the traditional German suits are leaves, hearts, bells, and acorns. However the familiar French suits (spades, hearts, diamonds, and clubs) were widely used internationally in the 30s just as now, so they wouldn’t be wrong.
Probably you need a full 52-card poker deck, but note also that smaller decks might have been popular in Germany, for games such as Skat (32 cards) or Jass (36 cards).
All the best,