Yeah it's annoying that we don't have a similar subscription service here, maybe the market for it isn't big enough. They do say on their website that they are working on delivering to new territories so possibly in the future.
If you are stuck and want to get your hands on tretinoin, you could try Farmacia Andorra, however the delivery charges to Ireland are 15-20 euros, so I tend to buy a few tubes at a time. Also once I ordered from them and it never got delivered, some problem with customs. But I contacted them, and once the package was returned they refunded me the money (minus delivery charge). Or if you have a good friend who lives in Spain, it's available over the counter in pharmacies (labelled as Retirides).
There is also Tretinoinworld, as recommended on here - do don't sell Retirides, which is the brand I usually buy, but Retino-A is supposed to be just as good, and it's the same strength so.
Just be aware, if you are sourcing it yourself to start on 0.025% and work up to the higher strengths (I'm still on 0.05% after 3 years because I like the results and my skin tolerates it well).
Also, if you haven't used it before, go slowly, maybe once a week at first and then after a month twice a week etc. You will still probably go through a crappy peeling/ irritation stage but when you come out the other side your skin should improve massively.