I don't think the original English version was ever released on DVD. I believe it was released on VHS at one time and you might be able to find someone who transferred the VHS to a DVD-R. You have to be careful not to buy the English version as edited for television.
Other than that, the best you're going to get is the Elvira DVD, which is the Spanish print (including Spanish credits!) with English dubbed back in as the audio.
It's a shame, but this extremely well-made budget horror film seems destined to be lost to history.