$5 and I will share. 
Just a sec have to go check my Amazon past orders.
Okay two options here. First below was used by another long-term member of the forum, and he said it worked very well for him. This one is Z-Wave only:
https://www.l-com.com/wireless-antenna-900-mhz-3-dbi-rubber-duck-antenna-rp-sma-plug-connector
Below is the one is the one I use. It supports both Z-Wave and Zigbee, and comes in a two-pack:
It is much bigger and much uglier than the other one, so if aesthetics are an issue, and you only want a new antenna for Z-Wave, I'd go with the first one. The one I use has a cable connect so you have more flexibility about where/how the antenna is mounted.
Bingfu 4G LTE RP SMA Cellular Antenna 7dBi Outdoor Antenna (2 Pack) Compatible with Spypoint Link Micro Covert Spartan Stealth Cam Tactacam Muddy Trail Game Camera Security Camera Wireless Router https://a.co/d/3UuqQ5n
Unbelievably, my wife has been OK w/these two mounted on the end of a bookcase in her office for many months. Truly have no idea why this is OK, but not going to bring it up w/her, ever. I initially had both antennas mounted, but ended up only using one of the them for Z-Wave, and kept the stock antenna for Zigbee. That combination worked best for me.
Both Z-Wave and Zigbee replaced:
Just Z-Wave replaced:
