Tow bar for an Auto Sleeper Harmony

I am trying to get a Tow bar fitted to my 1990 Auto Sleeper Harmony on a 1000p express van. 

A local company has taken on the work but tells me after 6 weeks that they can't find where to attatch a bar to because of the water bottle ! .

I have seen others fitted so it can be done. Can anyone help ? Thanks

The tow bar on my Harmony (Fiat ducato 14) is a simple affair consisting of two angle irons, one each side, bolted through the chassis and the tow bar bolted across the back...They effectively box the water tank in.....