Not hard at all! SN is not really a drug afaik so you dont need prescription for it. You can go to some local chem shop or check out online marketplaces for it. In fact, I received my SN a few hours ago :D
Edit: just noticed your title says meto, I'm assuming you accidentally wrote sn in your post so here we go
I couldn't find any pharmacies selling it without presc unfortunately (largely depends on where you live though maybe you can try it out in your city), but you CAN lie your way out. There are online services which can deliver it without questioning you too much. You can tell them something like, "I'm dealing with (insert a symptom meto is used to treat)" You can also say that your doc prescribed you this once and it worked for you or that your partner uses it and it worked for you when you took it