For the offical crew portrait photos taken before the launch the Apollo 9 crew wore full Apollo spacesuits but in place of betacloth patches they had embroidered mission patches loosely fixed in place.
The best-known of the official crew portraits, shown to the right, is S69-17590.
Fortunately, very high res versions of this photo are available which allow us to see which patch they were wearing.
The patches are clearly visible in the detailed images on the right.
Note the distinctive font used (particularly the "S"s) and the wide separation of the CSM and LM.
As with Apollos 7 and 8, when the Apollo 9 crew came on board the U.S.S. Guadalcanal from the rescovery helicopter they were wearing their betacloth overalls complete with betacloth crew emblems, but they did change into regular blue jumpsuits shortly afterwards and these had embroidered patches attached.
On the right are detailed closeups from two photos that show the patches on the jumpsuits on the recovery ship.
Although the lettering is not clear, the details of the design, especially the gap between the CSM and LM and the shape of the Saturn V rocket, appear to match those of the patch in the pre-flight portrait photo above.
This patch, worn by the crew on their spacesuits for the official crew portrait, and on their post-flight jumpsuits, is the one we refer to as the Apollo 9 Crew Patch.
A variant of the Crew Patch exists which has small but noticeable differences in execution (detailed in the individual patch entries below).
The photo on the left (courtesy of RetroSpaceImages) shows Dave Scott wearing an example of this Crew Patch variant on one of his flight suits a few days before the Apollo 15 flight.
Rusty Schweickart also wore this variant on one of his flight suits on the U.S.S. Guadalcanal after the Apollo 15 recovery, and examples of this variant were carried on the mission as souvenirs alongside the other version of the crew patch.
To further complicate matters, according to James McDivitt the crew returned a delivery of patches that were intended to be flown because they lacked the red "D".
What may be an example of this first version of the crew patch can be seen here. Apart from the lack of red thread in the "D" this patch matches the regular Crew Patch perfectly. A 'red-less D' example of the crew patch variant has also been found as shown here. Again, part from the lack of red thread in the "D" this patch matches the Crew Patch variant perfectly.
There also exist some versions of the Crew Patch variant which seem to be more crudely executed, and perhaps even fractionally smaller in diameter (by a millimeter or two), as can be seen here. It may be that these are pre-production samples of the variant.
Because the similarities between these crew patch variants far outweigh the differences, my feeling at present is that they represent examples of different manufacturing runs of the same patch, although the existence of 'red-less D' versions of both variants is difficult to explain.
The Crew Patches
Other Embroidered Mission Patches
3" Embroidered Mission Patches
 Examples of Apollo 9 Crew Patch sales:
 Examples of Apollo 9 Crew Patch Variant sales:
 Examples of Apollo 9 Crew Souvenir Patch sales:
 Examples of Apollo 9 Teaxas Art Emroidery (Oversize "Red-less D") patch sales:
 Examples of Cape Kennedy Medals 3" patch sales: