Question: I would like to buy only 4 capacitors like this:
750pF
1600VDC
500VAC
5% tolerance

I only find it on mouser but MOQ is 2'000; almost same as me !
How I can deal with that? Should I try to find 2 capaciters totalizing 750pF and wire them in parallel ?

Thank you

Answer: 
Try looking at parts with higher voltage ratings (when filling out the selection form select ranges)

a more durable capacitor should not adversely effect the operation of your circuit.

I found one on mousers site that was available in singles.
There are many places other than Mouser or DigiKey who sell capacitors. For example, [Tedss.com](https://www.tedss.com/2020085455). Did you try to Google for "Film Capacitors 750pF", or e-Bay? Here is another place for caps like that, [StudioSoundElectronics](http://amprepairparts.com/caps.htm).