Basically copy coupon, view price history or create e-mail price alert. Do you want to know what the best price is?
Aliexpress
There’re some similar (or not) items on Aliexpress
Click here to search by yourself. Here are coupons that you can use.
Latest price update (UTC time):
Input voltage: DC12V, fast charging): 1.33mA, Input current: max 1.35A, fast charge): max 1.35A, Output current: 800mA, fast charging): 15V, Output voltage (max, Material: PC, Output voltage: 12V, fast charge): 20V, Compatibility: mobile devices that meet the Qi wireless charging standard, Output current (max, Input current (max, 20W wireless charger, Input voltage (max
Banggood
Banggood warehouse is located in China. I found coupon for you. Check this out.
Link: Banggood product page
1. ($30.99): 13f142
you should apply the coupon in your cart after clicking “Proceed to checkout”. Click to copy code and open shop.
Exclusive Allowance Coupons: https://bit.ly/3xWgD9k and https://couponsfromchina.com/short/5cd
Old coupons (from the oldest to the newest): 502C6B, wirmik, esbgqi20w, TTxBG10, w20qiwi, aff7off, BGmipqi, BGqiwd, BGwirqi, BG2QIBP, BGPL20W, 2019SPEDM, BGXM20W, BG2qibp, BG3CSUM, BGmiqihc, bgssaff9, BGgrf1499, AFfbG10, Bgmiqi82, BGwirqi9, BG13thpl20w, BGqiw92, BGmiqic9, BG20qiwls, BGqi20mi, BGmiqi11, BG20WMI1, BGBFAFF2019, BGCITYADS2019, BGmi20wq, BGmi20w29, BG20wmiqi17, BG20wqihc, BGmi20wq1, 0e7f33, BGFCHRA, BGMWC30W, FBCOUPON1, bGhOnEy10, BGXM2W, BGXMI15, BGdragonBoat, BGSS10%SW, BGXiaomi20W, BGAFF10OFF, bgshOOp10, BGXiaomi20WAU, BgoFErTaSchInA10, BGHU0036, BgcLuBofErtA10, BGXiaomi10BRCN, BGXiaomi20WPadCZ, BGXiaomi20WPadCN, BG20CHARGER, BGMBCBLE, BG670eb1, BGHONEY2110, BG4b0090, BGf3ffc5, BG707d3a, BG8ee860
(there’s a little possibility that old coupon will work)
Other warehouses/versions
This item is available in 1 another warehouse/version!
1. Europe – Xiaomi 20W Wireless Charger [EU] ($-3)
Price history and price alert
Here is price history (for all/most countries) for Xiaomi 20W Wireless Charger.
Price records source(s): Gearbest, 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)).