[Fluorescence]

You can get bluetooth keyboards on aliexpress for under £2.

If dealing with that type of budget then scavenging is probably the better route especially as online payments may also be out of reach.

In general, as a frugal person, buying "converter" type hardware is rarely a win because mass produced things are so much cheaper than more trivial but niche things.

However, converter type things are often unused clutter someone would happily give away. Just yesterday I came across some ps2 to usb converters. I can't imagine ever needing one again...but imagine the horror of not having one if you did! I probably didn't need to keep two though...