You should take another look at IB's short inventory. The list is quite good if I say so myself: Japan Shortable: 1029 Listed for Trading: 3628 I suspect within the 1029 names available you'll find most of what you need. https://www.interactivebrokers.com/en/index.php?f=shortableStocks&p=shortable
If you trade Japanese futures, one point to keep in mind with Reuters is that they do not filter out rollover data. So their charts are useless as far as I'm concerned. Quick, eSignal, IB do filter their data. But if you trade only stocks, as you say it's not a bad deal if you need a wide range of information. If it's mainly good charting that you need, IMHO eSignal easily wins over Metastock. But to each his own in that area.
If your size is > $150K USD, contact our help desk via chat or phone and we'll see if we can source it for you. Sorry about the minimum size but we need to borrow a minimum size for special borrows and need to cover our costs. In particular, the stocks not on the list tend to be deemed harder to borrow and have higher borrowing costs.