I have a Vivitar 285HV, which I almost never use, and I could sell it to you at a reasonable price. It is basically in new condition. You can set the power manually and it has a zoom head with tele-norm-wide settings… I used it with the ebay triggers, so it should work for you, too.
If you should decide to buy Zoltan’s Vivitar 285 you might also consider acquiring two other items which will add considerably to the versatility of this flash namely:
1. A dedicated Vivitar mains power lead…so you won’t need batteries.
2. A very rare Vivitar 285 Vari Sensor Adaptor which allows you to use the Flashgun off the hotshoe but still retain auto exposure.
See pics attached below.
Also, I have a 285 Flash Unit but it is not powering up for me so it may need fixing. The two items above though are in great condition.
(needless to say I am not including the Pentax MX)
I got a number of units from the Dublin Camera Exchange for €30 each. They’re film ones, so aren’t good for digital, but I get great use out of them for multiple off-camera flash situations.
BTW Don’t forget to set the camera to Rear Curtain or 2nd Curtain Flash, otherwise the pre-flash used to measure the on-board flash exposure will set off the external units before the shutter has time to open,