Hey Donna it depends on what your after ? Meaning if you're in to sweet tangy candish watermelon then something as simple as Watermelon Clear LA would work just fine. http://e-liquid-recipes.com/flavor/29700
Also in that same territory yet having more of a realistic smell is Watermelon TFA http://e-liquid-recipes.com/flavor/670 and almost identical yet subtly sweeter is their Watermelon Candy TFA http://e-liquid-recipes.com/flavor/15492
I enjoy mixing them if I can't seem to get what I'm after w/ just one it helps to blend a couple together.
I really like Delosi Watermelon and realize you'd mentioned it being unavailable. If you're wanting a very realistic more rind and non sweet Watermelon then Medicine Flower is it. http://e-liquid-recipes.com/flavor/32410 available at ecigexpress under the name Lotus Flavors these are MF that have been rebottled.
Some other honorable mentions would be Capella sweet watermelon & double watermelon both are weaker and imho need support from another watermelon...I'd also say Red Summer - Watermelon FA would fit in this category as well.
Flavorah Wateremlon mild lightly juicy needs a couple drops of FLV Cantaloupe to me to really help boost it.
INW Watermelon is quite juicy and a lil tangy semi sweet I'd say has some rind notes but I really need to play w/ it more to get better acquainted.
I don't really care for FW's Watermelon it ruins more batches than has helped but to each their own.
I don't know where you are located but if you're in the states most of these flavors can easily be found at
ecigexpress.com ( I have trouble w/ their site or I'd put up a link ) even after clearing my cache it just spins for an eternity.
Good Luck !
And @ozo I'm excited to hear about these flavors