Hi paulette,
The Pentax P-TTL solution is a bit confusing, but here it is:
Get 1 ea Off Camera Shoe Adapter F
Pentax Off Camera Shoe Adpater F 31046 B&H Photo Video
Get 1 ea F5P Extension cord
Pentax F5P 3' Extension Cord for Off-Camera TTL Flash 37347 B&H
and get 1 ea of either the Hot shoe adapter F
Pentax Hot Shoe Adapter F 31022 B&H Photo Video or 1 ea Hot shoe adapter FG
Pentax Hot Shoe Adapter FG TTL flash adapter
The difference between the last two is that the FG only has an F5P port, and the F has a hot shoe plus the F5P port so you can also use a P-TTL external flash on-camera as well as the remote external flash connected to the cord.
You connect the appropriate Hot shoe adapter, the cord, and the Off camera shoe adapter, and you have a remote P-TTL cord. The advantage of the Pentax system is that you can also get an uncoiled 9 foot long cord F5PL, for more extension. I have an FG-F5P-F setup, and it's lightweight and very flexible, but I've heard reports that the adapters break after extended use, and it is expensive. . .I bought mine used from KEH -- you can look under Pentax flash accessories to see if they have any used ones -- stock changes all the time, and you might get lucky.
There are also one piece cord sets for P-TTL. I found these two at B&H, and assume that they work, and B&H is a reputable outfit, so I doubt that they'd carry the product if either were junk, but I can't say. I have a Pro-Line and it's heavy duty, but the cord is not very flexible, so it doesn't stretch to the claimed 3 ft length, and the weight of the cord plus the tension makes positioning the external flash on a stand difficult. These don't look like they have this problem, but the length might not let you get the separation that you might want.
Dot Line RPS TTL Off-Camera Flash Cord with Swivel RS-0444/1 B&H Vivitar Digital Off-Shoe Flash Cord VIV-FC-PEN B&H Photo Video
If you are definitely going to only use manual mode for the flash, there have been non dedicated hot shoe to hot shoe extension cords, but they are pretty long obsolete, so finding one might be a problem.
If you live in an area where there is an old time B&M camera store or a "professional" photographic store, they might have some old used equipment for sale. You'd be looking for a cord with:
1. one end with something that looks like the foot of your flash, but only with one contact in the center on one side and a threaded hole on the other side,
2. something that looks like the hot shoe on your camera with only the big center contact in the middle on the other end.
I found one of these a few years ago for about $5
Your last alternative is to find the same thing as the last thing I described, but in components -- a hot shoe to PC adapter, a PC to PC cord, and a PC to hotshoe adapter. This is probably what the local camera store tried, but with some Nikon components. I'm not sure why this didn't work, but here are some alternatives:
FAPC15 Adorama Non-Dedicated PC Sync Terminal Adapter (Hot Shoe to PC) HSA302 Adorama Adapter shoe mount & PC 1010302 PMPCMM Paramount 5' Coiled Sync Cord, PC Male to PC Male
You should be able to find longer PC male to PC male cords, but this gives you an idea of what to look for.
You could of course get one of the P-TTL alternatives and just switch the flash gun to manual mode. You could then also use P-TTL if you wanted to. . .
Scott