Map holder[

Does anybody know who makes a tank map holder? By the way my tank is plastic so any magnetic retaining bag is ruled out.
Baglux do one but it is expensive as it comes with a tank protector and works out at about ?100
I only want a cheapy as I would only be using it a couple of times a year
also looked at using Tom Tom as an alternative but don't know if the bike version has the same mount as the TT One.
A tank bag is out of the question as I find them obtrusve and I already have detachable solid pannier system for my kit


Any help would be appreciated