I agree that trying to get every plate of a pane of 20 of the low denomination stamps can be VERY tough. As I wrote getting S1 of the 2 cent Navajos is tough - I have gotten one or two over the past two years. Plates of P1 and S1 of the 1 cent Tiffanys are rarely found in my area - I have 2 S1 panes with two different positions and only 1 P1.
You can get them from stamp sellers but you pay a premium - I recall about $1.50 for the 2 cents panes of 20 from Bardo stamps. And yes you could ask around at
ebay but then the older plates risk coming in not so great condition.
And yes I was able until about early 2021 I got even the 5 cent Towleware American Design stamp until the USPS discontinued it and had it taken off stock at all post offices.
I am stepping up on my quest for the 1 cent and 2 cent plate positions (for V1 of the 2 cent and S2 for Tiffany 1 cent) as I think with a whole new set of designs planned for low denomination stamps in 2024 (1, 3,5 and 10 cents, note no 4 cent one). they may start to phase some of the American Design ones - they already have in the past few years with the 4 cent Chippendale (although there are ample supplies on the secondary market).
I do have a bunch of 1, 2 and 3 cent American Design. If you have some of the plate positions for the plate numbers I seek maybe we can do an exchange. Send me an email through this site if interested or let me know how best to reach you.
Good to hear that someone else shares a similar collecting focus. It is very fascinating comparing differences in the plates - the more dramatic case is the V1 2 cent navajo plate compared to the other ones.