If you're cleaning a sensor, the first thing to try is a good quality, powerful rocket blower. That will deal with 95% of spots, if you get the nozzle close enough (obviously you have to be a little bit careful when doing so). You might need repeated attempts, but it's worth trying, as any method that doesn't touch the sensor is best. If that doesn't work, then a gel stick is definitely the next step, IMHO.
The best choice for Pentax cameras is the official O-ICK1. If you can't get hold of one, a great alternative is the Eyelead SCK-1, which claims compatibility with the sensors used in Pentax cameras. I use the O-ICK1 on my own Pentax cameras, and it's excellent. I also use the Sony-specific version of the Eyelead stick on my A7 MkII and Hasselblad HV, and I'm very happy with the results.
I would advise against buying anything other than those two products... especially, avoid any unbranded or unknown-brand copies. And when buying the originals of either, make sure it's a boxed original product. You really have no idea of the composition of the gel on copy or unbranded versions, which could leave you with a much bigger problem than you started off with