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Enough for twenty or so - assuming you've got the means to saw file and drill.
If you're really stuck, let me know the dimensions you want and I'll make one: costs would amount to little more than a large letter stamp and pennies worth of metal from the offcut box. You might even find someone on here and local (to you) that could do it in a school / college workshop for free - even after Gove's interference, a foreigner (workshop terminology for unofficial outside job, not the other thing) will always take priority and be more interesting than education- one for 'Any Question Answered' maybe?
If you can't find any suitable L-shaped bracket things, you can always buy strip alu/steel from B&Q too