Artois was engaged to the prince de Condé's daughter, later Abbess of Remiremont. Or, with the right POD might even marry Mademoiselle de Penthièvre.
As to Provence, a Saxon princess is most likely. Zweibrücken was rather low on the totem pole - the children of Friedrich Michael were only heirs presumptive to an heir presumptive (which is why Maria Theresia refused to countenance a match between her daughter and Karl II of Zweibrücken). Friedrich Michael had an older brother, Christian IV, who had married morganatically, but if his wife died, he might marry dynastically. Christian IV was heir presumptive to Karl Theodor, Elector of Bavaria - again someone whose wife might die and he might remarry and have issue.
A dark horse might be a princess of Württemberg (OTL's Maria Feodorovna) OTL Karl II Alexander's sister had been considered for the dauphin after his first wife died, but Württemberg was unable to come up with the dowry. Marriage to the king's brother might not be so expensive. Likewise, if the margrave of Baden has a daughter kicking around, she's got connections at Versailles (the duc d'Orléans and family) who could weight the scales in her favour (but I'd put any German option besides Saxony in the outside track)