This is a manufacturer/supplier issue which goes all over the marker from pharmacies to underground stuff. Patches are very often out of stock here in Finland too and its some times absolute pain in the ass to get them. Also patches cost way too much to make even sense to use them, the only reason I do is that I've had them govt paid and right now I'm stocked as my gf gifted me many boxes of them as she didn't need them for now.
Injectable is the best way to ensure that you never run out of affordable estrogens, patches are the worst on the price, also not the best for maintaining decent levels, perfect for balancing the levels though and for minor adjustments, but if you play smart, do not become dependent on patches. Gel or injection is your best friend on DIY estrogens. Also don't bother with pills as your mainstay either, transdermal or injection is the best method for this anyway.
For stabilising levels, patches are great. For a minor boost when E is low before injection, gel is the fastest and super easy to use. For price, efficiency and longetivity, injection always wins. If you go that route, just learn to do it clean and you're good to go.

Oh this reminds me, I should some time write a guide thread about how to deal with injectable estrogen, I don't think there is one on this forum and maybe some ladies here would appreciate it.