Dan, your Ihagee is most likely 9x12cm, a relatively standard size in Europe. The "postcard size" is 10x15cm, almost 4x6".

An elderly 9x12cm or 6.5x9cm plate camera with a "cheap" triplet lens, or maybe even better an uncoated dialyte, can be had for very little money. Just make sure you get plate holders with film inserts with it - matching holders to camera tends to lead to having a big stack of holders and almost as many cameras.