We just got a lightweight sleep shirt from Downtownhoundz, and it's brilliant.
We also use small down throws acquired from Overstock.com. The nice thing is that they're light enough to be unimposing and maneuverable, warm but not hot, and the dog can always stick a leg out to cool off, kick it off themselves, etc. (Spencer usually has it in front of himself by morning and is using it to keep his feet and ears warm.) Here's the link to what we got a year ago; it's out of stock now, but you can put your email addy to be notified if they get it back, and it gives you an idea of what's possible (washability, size, etc.):
http://www.overstock.com/Bedding-Bath/Microfiber-Premium-Down-Throws-Set-of-2/5615629/product.html
You might consider a complete thyroid check, as those hormones tend to reduce with age and cause problems such as flipping of the sleep/wake cycle, increased feelings of insecurity, cognitive problems, etc. etc. On the other hand, a dog already on supplementation may need the dosage reduced in older age.
We've used the one-of-us-sleeps-with-the-dogs approach, alternating nights when possible, to good effect when we've needed to. No sense in both of you being awake all the time. Good luck, and keep us posted.