I have an impulse sealer (for heat sealing plastic bags) and it's no
longer supported by the manufacturer, which means that I can no longer
get the woven teflon material which goes between the heating element and
the plastic bags to seal
I'm sure it must be possible to get this on a roll , which would be
ideal, but my google-fu seems to be weak in that direction

You can now get non-stick sheeting in the supermarket - would that be
suitable ? (afaik its teflon)