Always a bit of a punt I know, but there are good sets on ebay as cheap as £16 for both front calipers.
But make sure the auction states that the dust seals are double lipped.
I usually buy two full sets (enough to do four calipers) on the premise that if any of the seals are not a perfect fit, they go straight into the bin and there are then more than enough replacements.
Still astronomically cheaper than OEM seals, despite the extra waste