I have the Yankee Hill Manufacturing 5C1 flash suppressor. It does an amazing job of flash suppression - from a huge basketball sized ball of flame down to nothing.
You indicated you also wanted some muzzle brake capability. The 5C1 is missing the slotted cutout on the bottom, which prevents dirt from being kicked up if firing from the prone position (less an issue for a PLR than an AR), but is also a fairly effective muzzle brake. The PLR doesn't kick much, but the 5C1 reduces the small muzzle flip to a very small muzzle flip.
I got mine a couple of weeks ago at www.globaltactical.com
, $21 including shipping, but they don't seem to carry them anymore. The YHM website shows them back ordered. The 5C2 will work, if you're planning on using it as a bayonette in hand to hand combat.
Here is one place that shows them in stock.
Try to buy a couple of extra crush washers to make it easier to mount muzzle accessories on the PLR, or send me a private message with your postal address and I'll mail you a nickel plated brass jam nut that'll work until you get something nicer.
The only down side I see to the 5C1 is the 1.5 inches it adds. That doesn't sound like much, but it's a lot on such a short weapon. It can adversely impact your carrying options. I still can't find a notebook PC case that fits, although that wouldn't be a problem without the flash suppressor. There are shorter flash suppressors and muzzle brakes, but I don't think the shorter flash suppressors are as effective. Some people like the great balls of fire.
Kel-Tec has a very effective muzzle brake, at least based on their video. Unfortunately, it remains back ordered.