There will be no less or more losses whether you use stranded or solid wire, the reason you would use stranded is for ease of use, it is much easier to work with because it is so pliable. The drawback is that the wire will not stay put once you bend it in a certain form, solid conductor will. Solid conductor, in your case, should be used because you are having a hard time trying to find stranded and it's only advantage is to save time! If you really have your heart set on stranded you should be able to get it from any wholesaler, I don't know where you are from but in Canada I would reccomend GESCAN or EECOL.
LEXX