Depends on how much you want to spend. You can take your chance on one of the cheap versions on ebay of the kit that has a software disc & the essential lead that contains the chipset.
But you will also need an old laptop that is running windows 7 32bit or older, the software will not work on newer windows versions.
I bought a cheap kit for £30, installed it on an old xp laptop. It took several tries to install it, there is a certain procedure you have to follow, the instructions were rubbish & I watched lots of youtube guides before I got it to work. When installed it is very buggy, sometimes refuses to load, freezes mid use & will rarely shut down normally.
There is a golden rule for the software - never let it try to update online. If it does it will discover it is a counterfeit version & it will no longer work. Unfortunately I clicked the wrong button one day & it stopped working, requiring removal and reinstallation of the full software again.
If I was doing it again I'd buy one of the good cloned versions from a uk seller with a full backup service & install it on a good used toughbook. There are sellers who will sell you a laptop with everything preinstalled.