I got a similar problem by being presbyopic meanwhile. I got a lot of cameras I would like to play around, that neither got diopter adjustment nor a lens attachment facility and for which I do not want to make a permanent lens attachment.

I thought of constructing a small number of attachments consisting of different frames and lenses (cut-outs from cheap plastic reading glasses), in order to have something apt for a variety of cameras.

Following Ken's idea I thought of using doublesided adhesive tape for that frame, with one side having permanent, the other reversible tack.