In most of my Campaign Settings, I try to emphasize that Magic is a rather Rare and Wonderous thing. You’ll seldom find Arcane Artifacts for Sale in Markets and generally you must locate them through Adventure. But some Settings are slightly less stringent and may make some Magic Items more available than others. You might have your “Ye Olde Magic Shoppe” conveniently franchised in most Settlements, or Characters might be able to purchase some things (like consumables) on occasion from a travelling Alchemist or Witch. Potions are consistently in demand, and a bit of a mainstay in these situations.
They may balk at the Steep Prices for such things, so here is another Option: They might be able to save a little Gold by going with a draught that’s perhaps a little less predictable or has some unusual drawbacks. Here are One Hundred Potions, with a couple ideas for these kinds of “Side-Effects” that might impact their efficacy a bit, result in a more challenging situation, or just simply add a little humor. As for how long these might last, I’d usually go with something Randomized, or maybe a periodic Saving Throw once the Duration is up to return to normal. Usage Dice could be useful here too. Bottoms Up!