Just poked around amazon for 125khz pet readers and this popped up https://www.amazon.com/dp/B07SFXPX6P/ref=cm_sw_r_cp_apa_i_qW1eEbVWC470D

Pretty ideal, just hold the crystal inside the ring and press the button. Tempted to paint it silver and kitbash it a little bit, make it look like an actual in universe scanner