Based on this product's specifications, here are some alternatives and similar models
Contract form set Michalczyk & Prokop D UMOWA-ZLECENIE A4 2-part 511-1U
Summary description:
Michalczyk & Prokop D UMOWA-ZLECENIE is a preprinted A4 contract form in a 2-part (duplicate) format, model 511-1U. Designed for documenting civil law contracts (contract for specific work/mandate), it provides two copies—original and duplicate—on ready-to-use sheets for administrative, freelance or small business use.