Vapesafe is the only place I know where you can buy single prefilled KR8 cartos to try.
BTW if your old cartos were not singed and open easily (cap comes off) then you could try refilling some fairly recent ones with new juice and try one of the methods for cleaning the older ones. Drying is the trickier part.
One cleaning video. if your cartos have an inner donut shape seal you need to remove that too.
YouTube - How to clean cartos
And for drying some people have success with blowing out liquid then putting them standing on end in a 175 degree oven for a hour or more. Attempts at plain air drying can end up with mildew and mold.
If you determine you definitely have a KR808D-1, then considering a manual battery as a spare in case you kill a battery with a leaking carto. LiteCigUSA.net charges under $10 for a manual KR8 280mah battery (the standard length).
And re research - I have better luck using Google to search ECF. Google is better at prioritizing the answers and much better at multiword searches. You can search like tis:
site:e-cigarette-forum.com white cloud
site:e-cigarette-forum.com white cloud KR808D-1
And unfortunately the ripoff rebranders have a whole seedy upper crust of ecig sellers that is very visible on the web, seemingly supported by lots of fake review and comparison sites citing why they are the best, fake experts, "testimonials", bs bs bs. But it is often what people find first.