The 'housings' are not replaceable in and of themselves. You need a new headlight. This can and will be an expensive process. There are several avenues you can go down. Aftermarket or OEM.
A new OEM xenon assembly, without the xenon parts is $950.00. With the xenon parts it is $1275.00. Aftermarket halogens are somewhere around $400.00 each.
IMHO, I would try to recondition your lenses first. If done properly, your headlights will look like new.
How does something immoral, when done privately, become moral when it is done collectively?
Furthermore, does legality establish morality?
Slavery was legal; apartheid was legal; Stalinist, Nazi, and Maoist purges were legal. Clearly, the fact of legality does not justify these crimes. Legality, alone, cannot be the talisman of morel people. - Walter E. Williams