One of my players had that exact crit! LOL. He was a Warrior Monk and Martial Arts was his only attack.
Anyway, you have a couple of approaches. The simplest and easiest (if you want it to be) is Herb Lore, Foraging, Region Lore. Let the players look for the necessary healing herbs out in the wilderness. There is a plethora of healing herbs that will reduce healing time, mend bone, etc. There are regions and "difficulty" to find the herbs. You can adjust that difficulty as needed.
The players didn't have enough gold? Did one of them have a magical item they could sell or trade? How badly does the player want to be healed? "I'll heal that arm for you, but you don't have the gold... hmm that +15 Mithril dagger is very nice." I've also sent players out on side quests in lieu of payment to a healer. Leave an item as collateral until you get back from the dungeon crawl with lots of loot?
How realistic do you want your game to be? Realistically, a broken bone takes a long time to heal and the bone can't be moved appreciably. My son fractured his arm. It wasn't a full break, but the cast kept the arm immobile for a couple of months even though the bone was healed. 30-50 days sounds reasonable for total healing as you said, however the immobility (-75) could be more due to the sling or cast the player wears, not so much from the broken bone itself. I caught my son several times with the sling off playing video games because it was easier to play without it (-75 to Call of Duty Skill).
The original crit was to the leg and putting pressure on a leg bone while it's healing could very easily result in -75. You adjusted the crit to reflect the arm damage for the sake of realism, but you should also adjust the penalty. For months after my son's arm healed, he still complained of pain when trying to lift himself off the ground or when carrying something heavy. I can only imagine that a broken femur would be much worse when supporting body weight, armour weight, backpack, jogging/running/dodging. Compare that to a broken arm and jogging/running/dodging.