Did you hook up one of those TI keyboards to your ZX81/TS1000? Don’t you wish it had all the Sinclair legends on the keys? Well, if you can find an old membrane keyboard (remember those?) you can cut it up and paste the legends onto the keys with silicone glue (RTV-Room temp. cure).
The membrane keyboards consist of three layers; the top layer, which has the legend artwork, a separator layer with holes and a bottom layer. Use an X-acto knife and start to separate the top layer, and peel it loose from the other layers with one quick motion to help prevent creases. Use a sharp pair of scissors to cut up the top layer into its individual “keys.” You’ll have to cut right along the top of the keywords, and along the bottom of the functions so that the “covers” don’t lap over the edge of the keys. Similarly, cut right along the edge of the white portion on the left and right. The corners have to be clipped also, you might lose part of the first letter of the keywords but cutting it close will help prevent peeling later.
Clean the keytops with alcohol and q-tips to remove any oils that your fingers may have left on the keys. This will promote adhesion considerably.-ed.
Put a dab of clear silicone cement on each key, one at a time, and push the appropriate cover on with the eraser end of a pencil. The excess silicone will squish out, forming beads along the sides; leave these alone until after the silicone has dried, at which time they will be easy to remove. Even if the keytops are curved (as they are on the TI keyboard), the “vacuum” produced will keep the covers in place until the silicone dries if you used enough to assure a uniform layer. When dry, tap each key with the pencil end of a pencil; any that are loose will make a distinctively different sound. Re-do any that are suspect, or that have obviously lost the “curve.”
You may also consider moving the keys around! This is required in order to have the keys make the most sense on the ZX81; for instance, the cursor keys on the TI are on D, S, X and E; move these to 5, 6, 7 and 8. Similarly, some of the other keys have other symbols on the front, which can go into whichever position makes the most sense on the Sinclair. Since you’re covering the tops, it doesn’t matter that they’ll be in the “wrong” position.