I rarely see the digitizer being sold separately. But it is easy to find LCD with digitizer. But it seems that iPhone 5/5c/5s replacement screens parts are out of stock in the market lately. May be you can look it up on other website.
i search on ifixit parts store, can't find any replacement parts for dell sreak, so i search for google, i found on http://www.dbx.com.cn/Products/OEM-DELL-Streak-mini-5-LCD-Screen-complete-1054675, i dont't know if this is the model that you are looking, hope this help you