Wheel lock, p/n 61012932000, about £350. This put a permanent attachment on your front brake, really low. These need to be kept clean, probably not ideal for offroaders.
You can get the exact same hardware, reference XRA-107, but in black instead of orange, from Roadlock instead of KTM. This saves a ton of money over the orange KTM version. But it is probably a good idea to get XRA-307 instead, as it fixes to the right side, which makes it more accessible when the bike is on its side stand.
Not that there are two sites selling this stuff:
roadlock.eu, which list the 790 Adventure explicitly with a price of ($200/€230/£132) plus shipping. Use the coupon 790ADV for a 15% discount.