A high powered LED flashlight will work wonders. They are relatively inexpensive and last quite a long time. You can find these in camping supply stores, and big chain stores (WallyMart).
Cup your fingers around the egg, like you would put your index to thumb (tucked in) to make a viewing circle. Put the rest of your fingers/palm over the flashlight & rim to hold it & block out the remaining light. Volia!
You didn't say what type of quail they are but with Japanese Coturnix you want to look for veins at around day 8-9 and the egg should be mostly dark at around day 14. Since you're close to lockdown, just look for which ones are the darkest inside. They're good. The ones that are half or less filled (as in, you can see much more light) are likely early quitters.
Best of luck!