I could suggest a Habsburg match in order to strengthen his claim to HRE and Spain... After all Henry IX would be first cousin to Charles V... Perhaps Henry IX could contest an Imperial election with better luck than his father...
Unless Spain was at odds with France and in serious need of English support, I think the Habsburgs will still prefer to marry the Archduchesses Joana and Maria off to Portugal and Austria. Henry IX's options of Habsburg-friendly brides would most likely be limited to a Portuguese infanta (huge dowry) or the Emperor's younger sisters Mary (born 1505, widowed 1526 when he would have been 15) or Catherine (born 1507, OTL wife of John III of Portugal - perhaps Mary Tudor takes her place as his wife?). I don't see any of these marriages really putting him in a position to challenge Charles for the HRE.
Alternatively he could marry within England - Margaret Douglas, Frances Brandon or Catherine Pole (heiress of Margaret Plantagenet, Countess of Salisbury, from the old English nobility Queen Catherine liked so much).