You could try Sebastian Remus.
E-Mail:
remusresearch@t-online.de
I've used him a number of times and the quality of his images is excellent. His charges (assuming they are unchanged) are:
EUR 0.20 per image
His time charge is EUR 38 per hour but quite often as long as he is given a large enough order, he'll waive the time charge.
He doesn't ask for payment in advance but doesn't release the images until he has been paid, sending out an invoice on completion of the work. You'll need to pay him by bank transfer. Files are then sent out by post on discs. He only accesses the internet via his mobile phone so for that reason doesn't send images via WeTransfer (or similar).
I've never had any difficulties with him even when I've given him requests to part copy a file. He was also very helpful to me in getting access to PERS-1 files and Fliegerkarteikarten.
Please feel free to mention my recommendation.