There has been a great deal of gloom and doom in the model railway kitbuilding community at the news that Mr Mashima has retired and no-one else is taking over the business. Some have been scrambling for Chinese alternative on eBay, others are just adding "can't get a motor" to the list of reasons never to consider building a kit.
Aside from several gearbox manufacturers having stockpiled Mashima's for a while so they can continue supplying, here's the first complete alternative that I've seen on a stand at an exhibition. In this case, York last weekend. No doubt there are others, I've just not spotted them yet.
The motor and gearbox is in the Comet range, now sold by Wizard Models. I can't comment on the effectiveness other than to say Andrew know his stuff and doesn't sell rubbish. I've certainly use one. Hope this helps someone.