If you think about it, any black and white negative film can be processed as positive. After development but before the fix, you bleach out the developed silver. Then flash the remaining unexposed & undeveloped emulsion, develop and fix. This is essentially how all positive film is created. Best to start with individual sheets of film just to get everything down.
If you don't want to do that, you can contact print your negatives onto new film and process that (shortening the processing time so contrast doesn't get out of hand).