Fiend territory, some active traps and a couple mine boxes inside and outside. Also, the sign shop in the exterior cell just before going into Vault 3 has some minds.
H&H Tools has some as traps, so be wary.
The region around the Abandoned Bunker between Forlorn Hope and Nelson has mines left from the original release of New Vegas when they had NPCs with missing limbs begging for death. (Removed due to lag issues)
The most abundant is the Lonesome Road DLC as you can fine the unique mines in Lonesome Road all over and if your explosive skill is high you can make some mines of your own as well.
Besides buying them?
If your concerned about the DC's, Harper's shack may not be the best place to hang your hat. Couple that with the respawning Vipers in the area...
You can make tons of bottlecap mines if you remember to pick up the lunch boxes you see everywhere. If you have the DLCs, you can get Satchel Charges in the Lonesome Road and those are just as good as frag mines.
You also want the Explosives Expert and Splash Damage to get the most out of your mines.
Satchel charges are a good explosive to use.
If you're willing to be pragmatic, win at the Sierra Madre tables and break the bank. Hoarde your chips in Dead Money and convert them to Pre-War money at the cashier's desk and when you get back to the Mojave, use the winnings you get in the safe every few days to convert into meds you can sell. Some might call this 'meta-gaming', but if you want to take full advantage of things without exploiting (IE getting all the gold out the Vault), then this is a perfectly 'legal' (IE no cheats) way to do it.
Oh, in ways you can only imagine. Lonesome Road is best left for last. A better (and safer) survivalist shack would be the one by the Yangtzee Memorial.
Bradley's Shack is nice. Hell's Motel next to Mesquite Mountains Crater is good too.