The only thing I know of is tension rods, which fit inside the window frame.

Thanks. That was my first choice but the window already has 2 inch faux wood blinds which take up the space I would use for a tension rod. The problem is that this is the guest bedroom, and there is a street light outside that shines in on the bed (only two ways to place the bed and both result in light on the sleeper). So I also need some kind of drapes and this is the only idea I had.

Have you considered something like a Japanese screen that could be moved in front of the window to block the light?

Oh, I know what you are thinking of - those things that go on the corner of the frame.

Here is a link that might be useful: Instant up

The Levolor Twist and Fit rod is a funky rod that sticks out from the window frame but is held on by a skinny tension thingy that presses onto the inside of the frame that should fit with your wood blinds. Comes in black, "cocoa" and satin nickel but I'm sure it would paint up fine if you wanted another color. It's at Walmart and a bunch of places online - Google it. Cheap, too, at around $10 for a 24-48" size.

I used a Twist and Fit from Walmart once and it worked great.

Here is a link that might be useful: Twist and Fit rod

Have you thought of using the really big Command hooks? They have them in a brushed nickle finish. You could mount them on the wall on either side of the window, then use a decorative brushed nickle rod laid in the hooks. I have always been very pleased with the way that Command hooks hold and then release without a problem.

The link below has all of the available hooks and a coupon for $2.50 off the metal hooks.

Here is a link that might be useful: Command coupons

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What a great idea! No, I had not thought of them but the jumbo can hold 7.5 pounds so that should do for reasonably light fabric. Thanks

Note the coupon expires 6/22.

I used Command hooks once when I "test drove" hanging an antique kimono over my bed. The hooks worked fine, the kimono didn't.