The only one I've seen, is the one in the video. It was discussed at length on here a couple of years ago.
Plus side is no VCU to worry about.
Down sides are cost, not automatic in operation, and can only be used when the tyres have low traction. The front and rear diffs on a Freelander are geared differently, so whenever this lock is engaged, the transmission will suffer from wind up, making use on slippery surfaces essential.
Stick with the VCU, fitting a Bell reconditioned unit if necessary, and make sure you have identical tyres all round.