Haggis doesn't have them any more i bought them both then sold the redundant one on ebay
I did noticed the possible prob with that style too ,i looked at redrilling the cap at an angle[i was wanting to use a headlock]CK though i wouldnt try that you'd just wreck,
Another option i thought of ,was to take a 20mm headset spacer ,then grind it at an angle, thin at one end,thick on the other,place it on top of the stem then add the cap,you'll prob need to use a longer bolt,but its the only soultion i can see
the main trouble you will have is how to safely hold the spacer as you grind it ,you could hold it between two pairs of pliers,but i'd make try to get it on the end of a length of dowel [a 4" length of brush handle will do] ,force the spacer onto the end of the handle,you may have to reduce the diameter of the handle to make it fit
When its on securely, press it against a bench grinder ,grinding down the metal and the wood at the same time,use a marker pen to colour in the required angle
you could also use an oil stone to 'fine tune' the angle once the heavy grinding is done