Admittedly, the idea of short term accident insurance plans is absurd. Effectively, you are planning to get into a qualifying accident and die or become dismembered during a limited period of time. No short term health insurance or life insurance company in their right mind would sell you such a policy; they are basically guaranteeing their losses!
Moreover, intending to use your accident insurance that soon implies suicide or purposefully risky (not to mention possibly criminal) behavior, neither of which no accidental insurance covers.
Hypothetically, if such a plan were available, premiums would be extremely expensive. That would be the only way insurance companies could possibly recoup. If you are at serious risk, you should buy the shortest term of accident insurance available. However, that term will probably be five years at the very least; on the other hand, temporary health insurance coverage can last for as little as one month.
