that $1200 ebay seat has been listed for months...... I wonder why?
Foams and covers are readily available, but a solid seat pan can be a bit difficult to find, and can command some pretty high prices.
You mention a '70 H1a?
There is no such thing.
1969 H1
1970 H1
1971 H1a
1972 H1b and/or H1c
While all 4 years ('69-'72) are interchangeable as far as mounting goes, The '69 and '70 seat pans are identical, having no "document holder" tabs being punched into the pan. The '71 and '72 pans have these 4 tabs punched into the pan for the clear vinyl/plastic document holder.
It isn't terribly difficult to turn a later '71/'72 pan into an early pan by folding these tabs over and welding/blending them in....nobody would ever know.
A little more difficult however to accurately "punch" the tabs into an early pan to make it a '71/'72 pan, but Im sure somebody, somewhere along the line has done it.
If your friend isn't super picky, I believe Z-power (in Europe) sells a full fiberglass pan -repop- seat for a reasonable price.