The wiki page recommends this bit which should be available at your local home depot: https://www.homedepot.com/p/Diablo-1-4-in-Up-Spiral-Router-Bit-DR75101/204073552
If you have enough time to order bits, I would strongly recommend the single flute 1/4" bit offered in the Maslow store: http://www.maslowcnc.com/store/singlefluteupspiralbit
The maximum feedrate for the machine is currently lower than a two flute upshear bit needs to avoid excessive wear. A more in depth discussion is located here: Increasing the Max Feedrate?
I also have ordered my bits from Thinker and Tinker, they have a good selection of tooling for various applications and I like the quality of the tools they offer: Application: Woodworking
Good luck on the build! It’s exciting to get to building and running the machine! Please post your build and any feedback you may have. It’ll help future builders too 