Play-Asia is selling a PS4 to Switch converter which will allow you to play your Nintendo Switch with a PlayStation 4 (or even a PS3) controller.
Priced at around £20.00, the Brook converter is cheaper than a Switch Pro Controller, and it’s also compatible with a range of PS4 fight sticks such as the budget Venom arcade stick. A list of compatible controllers can be found on the Play-Asia site under ‘description’.
The Switch Pro Controller is quality, but it’s also pricey (about £55.00 on Amazon). If you’ve got lots of PS4 controllers and fight sticks like I do, this converter may well be worth considering.
Play-Asia is a trustworthy site I’ve used many times to import games and Amiibo from Hong Kong. This converter is also available from Amazon UK for a higher price if you prefer:
Gam3Gear Brook PS3 PS4 to SW Nintendo Switch Super SW Controller Adapter with Gam3Gear Keychain