Tk102 sim from datasims and monthly contract of £3 a month with it you can set it up for differant types if settings and basically you call it then sends you map coords of where it is or you can set it up others ways, recommend buying it with constant power supply and hook it somewhere that gets a perm inset live feed, they come with waterproof cover , magnetic back and battery's but these tend to last two three days hence hook up to live fed constant . Price depends where you buy one from , wish.com to eBay around £10 to £15 plus cost of sim if not supplied with purchase usually £3 from datasims .
Hth
I have two in use for past few years.