In the US, you can get 50000 IU on Amazon, good enough for weekly supplementation if you're low (same as prescription strength).
I'm certainly not going to put something from amazon in my body. God only knows what you're actually getting
Also what's an IU. Apparently it's meant to normalize impact across vitamin D species of which there are multiple. Part of me can see the reasoning but it runs contrary to how much of medicine/pharma operates, generally in such form as either mg per time interval or mg/kg per time interval. It would be like taking the whole armada of blood pressure drugs and dictating their doses in mmHg instead of milligrams. If only things were so simple!
I just got more 5000IU at Walmart which was a nice surprise. Normally I take two 2000IU tablets.