Promaster makes a series of P-TTL compatible flashes. Generally, their distribution channels seem to be smaller than others (as they were focused around small brick and mortar camera stores), and consequently they're a bit hard to find and perhaps more importantly hard to find at an attractive price point. Still, there's a couple of unique features which may make them worth considering.
Warning: The 7500EDF flash is the only model that works with the Pentax K-7, K-x, or K-r camera bodies. You will need at least firmware release V3-310, which should be the default in all currently-shipping units. Without this update, it will just fire at full power in all conditions. If you have an earlier version, the update can be performed (for free) by Promaster Service — contact them for details. In August 2010, Promaster stated that they were working on an update for the 7200EDF and 7400EDF, but more than a year later, that has not happened. Promaster has not tested the 7500EDF with the K-5.
- 7200EDF — a basic P-TTL-dedicated model, roughly comparable to the Pentax AF360FGZ in power.
- 7400EDF — another dedicated model, this one with a motorized zoom.
- 7500EDF — Promaster's top P-TTL-dedicated model which adds more power and features, including a swivel head and a secondary reflector.
Note: Promaster has added a few more models to the lineup, the FL1, FL100, and FL120. I'm working on getting more information on these
As with the Sigma flashes, firmware upgrades (if available) must be performed at the factory.
The module-based models require the 5050DXR/PX digital flash module. Because this module hasn't been updated to work with flashes newer than August 2008, these flashes may have limited appeal. There were three in the lineup, 5250DX, 5550DX, and 5750DX. Only the very simple non-zooming 5250DX appears to be still available. There is a manual-control module that can be used, but in that case a manual-only flash is probably more cost-effective.
Promaster also has a macro ring flash, the MacroLume TTL Digital. This is module-based, and uses the same modules as the 5000-series flashes.