If you can't for whatever reason do that, an eccentric heel drop is the exact same movement.
But, since it's come up, folks have asked for some decent videos.
I'd first suggest listening to this podcast by the (insane) Doctor Håkan Alfredson [P.S. podcast at new location] who invented the eccentric heel drop while trying to rupture his Achilles' tendon so his boss would have to operate on it and relieve him of his Achilles tendonopathy. Instead, he cured it. Whoops.
Having done that, and determining that you most definitely do not want Dr. Alfredson scraping your tendons to sever the nerves, you can try his exercises.
The videos below are the training for a study to evaluate the usefulness of orthotics for treating achilles tendinopathy.
"Achilles tendinopathy is a common condition that can cause marked pain and disability. Numerous non-surgical treatments have been proposed for the treatment of this condition, but many of these treatments have a poor or non-existent evidence base. The exception to this is eccentric calf muscle exercises, which have become a standard non-surgical intervention for Achilles tendinopathy."The videos look useful, and are based on Alfredson's protocol. I'd skip the marshmallow shoes shown in the video, and do them barefoot. I'd also avoid orthotics... But that's just me. (I'd also avoid taking any medical advice from any doctor from Latrobe University, where this study is being conducted, as the quack Dr. Payne is a professor of podiatry there. I'll not link to Dr. Payne's site again, but you can find it at the bottom of that link.)
I'll also note that Dr. Alfredson says that the bent-knee heel drops are crucial. Did I mention that you should listen to his podcast before trying out these exercises?
One more observation: I'm not a doctor, or a physical therapist, just a foot-deformed westerner trying to run the way I was born to. Also, you should never believe anything you read on the internet, it's all crap.
OK, now that the caveats are out of the way, here are the videos. I'll note that the videos are also available for download in the study (search for m4v in that page).
P.S. Lest you think I'm being too tough on Latrobe, and podiatrists, Dr. Munteanu, who is conducting the aforementioned study, has this advice:
"...If you are a runner, ensure that you have your footwear professionally fitted and replace your runners [sneakers] at least every 500km/6 months...."I wonder if that's been shown to be effective? Anyway...