My Amiga 1200 keyboard had 12 - 15 keys pads that were failing. I found replacements keys on many websites and were $2 to $4 plus shipping, too much, $30 - $50 to fix my keyboard. Note these are old used pads and may fail in a short time.
I found $5 to $12 to do all keypads many times. This will work on all conductive pads round or rectangle. The circuit membrane must be good, and all keys must work to some degree.
You can check the pads with an ohm meter on 200-ohm range and must be 80 ohms or lower across the black conductive pad to be ok, use slight pressure not to damage the pad.
Tools and parts.
1 Small tweezers.
3 Small roll of aluminum tape used on forced air duct systems. You can go to a business that does heating and AC and ask them for a 20 mm piece. It MUST be aluminum and have zero ohms across the foil.
4 Caliper or a way to measure 7.5 mm x 2.5 mm.
Wipe the circuit membrane with a paper towel to lightly clean the black conductive pads, do not rub.
Cut the aluminum tape to the size above, use the tweezers to remove the paper from the aluminum tape and apply it to the bad keypad and press it down.
Do this for all bad keys.
On round keypads you may be able to use a paper punch, but small squares will work.