@JustLuthor Cruisers come with A&A 1914, so you don’t need to find more (it’s destroyers that the 1914 fleets lack, but that’s a different story).
HBG sells cavalry units, but they come in the G40 colors as they are meant for GW '36. You could buy a bunch in white and paint or dye them, though.
If you were interested in destroyers for a WWI game, HBG also sells torpedo boat destroyers (essentially, obsolete destroyers from WWI) for GW '36, with the same drawbacks as the cavalry from HBG.
As for bomber units, the best I know to find some would be to find some on Shapeways. The HBG store there has a variety of WWI bomber designs. The drawbacks there are that buying 3d printed units can become quite pricey and they are not usually available in the color you might want, so more dying or painting for you.
My 2 IPCs, anyways.