Size: 27.5*18*9mm, dB: 100dB, Item name: AR TRACKER 100dB Beeper, Weight: 5g.
Just check coupons out (with price alert and history). Best price?
Aliexpress
There’re some similar (or not) items on Aliexpress
You can use link bot to get even lower price:
Click here to search by yourself. Here are coupons that you can use.
Latest coupon code price check (UTC time):
Banggood
Banggood warehouse is located in China.
Link: Banggood product page
1. ($15.93): BGGAL8
2. ($15.93): BGJON8
3. ($15.93): BGRCParts8
4. ($15.93): BG1efeb0
you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Additional Banggood coupons: first page and second page
Old coupons (from the oldest to the newest): ARTT, 502C6B, Parts8, AFfbG10, BGVDay10%off, BGAFF10OFF, bGhOnEy10, BGdragonBoat, BGSS10%SW, bgshOOp10, BgoFErTaSchInA10, BgcLuBofErtA10, BGCuponation10, 13f142, BGHONEY2110, BGDAVIS, BGRACING1125, Tabby20
(there’s a little possibility that old coupon will work)
Price history and price alert
Price history (for all/most countries) for AURORA AR RC Tracker 100dB Beeper is here. The lowest price was: $8.49.
Price records source(s): Banggood
Click on image to enlarge. 
You can set price alert (for Banggood and Aliexpress (only if product name will be the same as on Banggood and I will post it on social media though, so it’s more like Banggood price alert)).