Any major crystal vendor can make fundamental mode crystals. Contact the following crystal vendors to see if sample stock is available for customers to build prototypes:
- Statek: http://www.statek.com/
- Rakon (C-MAC): http://www.rakon.com/products/families
- Abracon: https://abracon.com/product-lineup/timing-synchronization
- Mtron PTI: http://www.mtronpti.com/products/Oscillator