Not sold in pads to my knowing, but you may wish to try Masa paper. It's a very thin (but very robust regarding its weight) paper that works well (= no problems + great density) with all the iron processes. (Cyanotypes, Vandykes, Argyrotypes, Kallitypes, Pt/Pd...) See this for instance. (USD 1.28 per 21x31" sheet... Actually, when I first purchased this paper a couple of years ago, it was only USD 0.75 per 21x31" sheet - anyway, it still has a very very good price; 1.28 / 4 = USD 0.32 per 10.5x15.5"...)