What portafilter basket options do I have for a ECM Rocket?? The OEM double portafilter basket seems too small...

I do use a bottomless triple but would like to still use a double but with a different basket.

What portafilter basket options do I have for a ECM Rocket??

Lots. There are probably several souces for ridgeless doubles baskets - here is one: http://www.espressoparts.com/ You can use that same source and others for a standard ridged LM doubles basket. Some impressive baskets are also available here: http://www.espressoresource.com/

If you typically use 16g or less, you really need a ridgeless basket to have a successful tamp with the typical 58 mm tamper. The LM basket works well with 17g or more. The 16-17g range is sort of a fuzzy category depending on the bean. If you do a site search on "baskets" or "paradox" - you may end up here:
Paradox: The LM double basket

Eric, I purchased a Ridgeless Marzocco/Synesso Style Double Portafilter Basket from EspressoParts. Thoughts?

Thoughts?

Sure. It is a good basket but I would have bought more than one and I would have even added two LM ridged doubles baskets to the order. The LM baskets are slightly taller and thus hold more coffee than the ridgeless doubles so when you are getting up there in doses, they come in handy.

Eric, is a LM basket referring to La Marzocco Double Portafilter Basket??

Eric, do you have a link to the part on espressoparts.com for LM ridged doubles?? I can't find it?

I'm not Eric, but see their portafilter baskets page. The most commonly referenced ones on this site are the La Marzocco double basket (ridged, also sometimes called "wasp waist" because of the shape), standard Faema-style basket (comes in 12 and 14 grams, though the 14 grams model actually holds more like 16 grams), ridgeless double, and ridgeless triple.