You'll probably have to purchase the chain and sprockets individually .
There is a 47T rear on ebay currently Auction # 114330197087 .
Parts Unlimited do pattern rears . They look a bit different to
the original Yamaha sprockets , but work just fine .
44T  K22-3621  or 47T  K22-3623 . However both those are currently
out of stock , but expected to be available in 3 weeks odd .
The 47 T sprockets will gear your bike down a bit , but if you fitted
a 15T front instead of 14T , you'll be pretty close to original gearing .
I don't expect finding front sprockets will be a problem .

Will a sprocket from a CT2 fit for a DT1?   Anyone know this?

CT2/3 sprocket is completely different .
The CT sprocket is pitched for a 428 chain , while DT1 chain is 520 .
That is apart from the sprocket hub , 4 bolt and 6 bolt respectively .

Thanks Swoop56.  this is great to know.

 
Really enjoying your adventure on this bike.
Speed and Sport lists a couple different size sprockets for both front and rear in stock for 68 DT1. 
Might find different sizes available on partzilla.
 

You could also try PBI (pacific northwest area), Rebel Gears (TN), Sprocket Specialists (UT), or other sprocket companies...  usually rear sprockets are made from hi-strength aluminum and not steel like original but they make good products and should have whatever size you want.  Front sprockets are always steel.

Thanks again guys great leads.   

I passed my inspection and can now register my DT1 for the Road.   That was by far the worst part of my whole restoration and I learned a lot about what it takes to get a vintage bike over the finish line.   Thanks to all those who helped me with this and I am looking forward to finishing my CT2 and DT2 over the coming months.  For now I just want to ride this bike down my old neighborhood and pretend I am 16 again....   One more thing off the bucket list.

Congratulations! 

And have fun! 

"Sixteen Again" , great song.

RIP Pete Shelley.

Buzzcocks-16 Again OGWT.14-11-1978 - Bing video