For router bits that I plan on using regularly, my go-to company is Whiteside. Uniformly excellent products.
But for something that will have limited use, I like the Amazon brand “Uxcell”.
While I cannot speak to durability on these bits, (I tend not to be using them often), I do find that they are produced within specifications and that they cut well. I have only bought their carbide tipped bits.
I just looked at Amazon, and their 20mm bit is $10.99, as a Prime member I get free shipping. If you are not happy with the bit, Amazon will take it back.
It should have no difficulty cutting 60 holes.