HIC bars have to be steel as they have got to have a relatively thin diameter, and as steels stronger you can go thinner than alu. If I'm correct there are no such things as alu hic bars as they'd have to be way to thin and would be weak as fuck.
you can buy Cropley HIC bars which are like 40 quid, and mr h HIC's which are like 90, and the lg pro ones although they've never replied to me over them. Bat wings would work too.