I don't use them because of the low capacity of LiFePO4 in such a small cell.
But if I did need them, because the gold standard AW brand blue cells are no longer available (factory flooded and AW never came back), I would get the
SureFire SFLFP123 Charger Kit with LiFePO4 charger from Battery Junction, along with a set of
extra cells.
Nearly every battery manufacturer lies about capacity. Surefire's capacity rating is probably dead accurate, and they are intended for high current lights, so that supports that these are good cells with an accurate capacity rating. You may see other cells, such as from Soshine and Tenergy, claiming to have more capacity. Don't believe it, they're basing their rating on low current applications, and they likely top out at 400mAh. I haven't seen any verified capacities for these sized cells in LiFePO4 over 450mAh.
Generally, when it comes to Li-ion cells, only buy cells labeled by known good manufacturers from known good sellers, because there are a lot of counterfeits and crappy labels.
That means, in no particular order, Li-on cells made labeled by Surefire, Samsung, Sanyo/Panasonic, Keeppower, Vapcell, Sony, Molicel, Imren, Efest, or LG.
Avoid Ultrafire and especially Trustfire, and pretty much any name with fire in it other than Surefire, and apparently Fandyfire iirc, CPF members have said was decent.
And only sold by Surefire, Battery Junction, illumn, Liion Wholesale, 18650 Battery Store, and IMR Batteries. There may be other quality sellers, but I am pretty sure about these sellers and know for certain that Surefire, Battery Junction, illumn and Liion Wholesale are definitely good.
I have had good luck with getting only those name-brand cells (specifically Keeppower) off AliExpress, and with Alibaba you can order direct from the manufacturer (such as Keeppower or Vapcell), with caveats like large minimum orders, so presumably the actual manufacturer isn't going to sell you counterfeits.
You can get a charger that will charge both 3.6V/3.7 and 3.2V cells, as well as polymer 4.35V cells and NiMH 1.2V cells, and they aren't too expensive, such as a
NiteCore D4 (this is the previous gen, which is less expensive while supplies last), which will automatically detect NiMH 1.2V and Li-ion 3.6V/3.7V, but it requires manually changing the charge program for LiFePO4 3.2V and polymer 4.35V. Since you already have a Li-ion charger, and your need for these cells seems to be specific, you may as well get a dedicated LiFePO4 only charger, and though I don't know that Surefire charger, I can only assume it's fine for their own cells.