Home centers will have these in several brands. You need to measure width and height of the openings you have now. Measure from concrete to concrete or block to block. On the top you probably only have a wood plate running across the top, so measure just up to the bottom of the wood plate. Take those measurements into the home center. If you are doing this yourself, I would just order 1 window and try it first. If it works out well, get the remaining windows.
For you also do search for custom windows.
An odd size you also do that for custom windows.