I don't own a PCP, but was considering purchasing one which is how I ran across the Shoe Box compressor. More recently, I was watching a YouTube video by Air Guns South Africa (if I remember correctly). One of the episodes he does some reviews of his equipment and has another brand of compressor (don't remember the brand), do some price checking.
Consider how much you use your PCP, while it would be cheaper and more convenient to have your own compressor, consider how long it would take to offset the cost of the compressor.
I've even seen homemade rigs that hook up a motor to a hand pump. Be careful if you go this route, hand pumps build up a lot of heat even using manually. I know they suggest stopping after so many pumps to allow cooling. This will be even more important if being operated by a motor as it will cycle faster.