Use your google-fu for a list of outfitters and/or boar hunting in Spain.
Where are you going to be?
There are a lot of boar in the northern regions. Be very very very clear on what you want, because the trophy fees can be extremely expensive. Sometimes in the thousands of dollars even for trophy boar.
Oh yeah! Make sure you go in the fall when they're fattened up on "bellotas" or accorns. The hams from those pigs - "Jamon Serrano, Pata Negra" - can fetch up to $2000!! Jamon=Ham Serrano=of the Mountain Pata=foot negra=black. Thus, black footed mountain ham. Named such because the wild pigs have black hooves. A ham can take 2 years to cure. AND GOD ALMIGHTY they are GOOOOOODDD!!!
Jesse had link to Der Spiegel which stated that in France 500k wild pigs are harvested and 450k pigs are harvestred in Germany. It might be cheaper to hop accross the border to france they must have some wild pigs in the Perynees. Perhaps the price for a bow hunt will be lower then Spain. If you have a chance maybe a private land owner would let you take out some piggies with a bow since the pigs are a real nusiance perhaps an add in local paper would work.
My cousins in Italy used to hang hams to make prosciutto. Pretty amazing stuff, but I think it takes about a year to age properly. So don't expect to make any sandwiches from a pig you shoot there... ;-)