Where did you get the pot control? It doesn't come with the vfd does it?
The pot specs for VFDs are usually pretty flexible. The exact resistance value doesn't normally matter very much because it works as a Voltage Divider, not a resistor per se: The ends of the pot are connected to positive and negative so there's a Voltage gradient along the pot and the wiper picks up the Voltage according to how far along the pot it is.
I usually look for pots in the 5K-10K Ohm range. You want them to be progressive and reasonably easy to turn without being loose, which means you need quality. Good pots tend not to be cheap new. They need to be Linear taper. Pots come in Linear or Logarithmic taper. Logarithmic taper pots are used a lot in Audio applications and are definitely not what you want.
The best ones for VFD control are designed for panel-mounting on industrial control panels and have screw terminals on the back . This makes them very quick and easy to change: important if you are trying to get an industrial production line back into operation (saving a few minutes of downtime on a production line making a thousand bucks an hour is well worth the extra thirty bucks or so for an industrial pot). The prices are not really justified for our applications though. I use them when I can get them free off scrap machinery. They are usually single-turn.
Otherwise, I tend to use 10-turn pots with either 6mm or 1/4" shafts from Bourns or Vishay/Spectrol, bought from ebay, particularly when putting together VFDs for other people. I use 10-turn knobs with counters and a lock, which makes it easy to set the speed at a known value. They are a minor pain to fit because the mounting is a bit more fiddly than the industrial ones, and the connections are for solder.
When putting together VFDs for my own use, I've been spoilt by the industrial single-turn ones and really find the 10-turn ones too slow now. I use my stash of single-turn industrials. If you have not used the single-turn already (and done so enough to expect that all VFDs will be single-turn), I'd strongly recommend going 10-turn. I've not found a non-industrial single-turn that feels anything like as progressive and rugged.
I generally pay around 3-5 GBP (about 5-8 bucks) for the 10-turn Bourns/Vishay/Spectrol with knobs on ebay, but tend to buy them when I see them, rather than when I need them in a hurry. I'd expect to pay rather more if fast was important.
The majority of the Industrial ones I've had have been AutomationDirect ECX2300 units. They match 22mm Telemecanique pushbuttons. List price in the US for these is around $36, but I have no idea how this relates to the price delivered.
