As soon as I found that I wanted a ROIDMI charger/transmitter cos my cars tape deck was broken to use the cheapie 3.5mm cassette method, conveniently all the deals around then had finished or I missed them.
In my quick check every few days I've found it's back on sale at Gearbest for ~$13.78. Looks like one of the cheapest prices for this item from a quick search!
Update: price increased to ~$15 even though the "sale" is still on
https://www.ozbargain.com.au/node/333428#comment-5149225
Don't buy this if you want clarity when playing your music file. I find the sound quality similar to listening to AM radio with lots of sound interference when traveling in the city traffic.