As anyone here can see the options are almost endless and range from lowcost to pritty expencive deals.
The best way would certanly be to get the SCSI module as you will not only get a nice and strightforward interface for the CDRom but also for other SCSI hardware... downside is the cost... well worth it if you need SCSI for other things, a bit too expencive just for CD support.
The easiest way would probably be a PCMCIA interface such as Alfa Data CD1200 witch should be quite cheap, or Artchos OverdriveCD witch can be expencive (and I've owned these and the cable from the PCMCIA to the CD isn't hi quality and do easily fail), or Sulf/Squirrel SCSI controller witch is almost as expencive as the SCSI solusion for your turboboard (and also with the same cable problem as Archos OverdriveCD).
The cheapest way would be to get hold of a 2.5"->2.5"->3.5" IDE cable and use it with the internal IDE controller... problem here is that you need to get the IDE cable outside the case somehow and that usually meens modding, also the internal SCSI.device doesn't support ATAPI devices so you need some drivers such as Idefix or AsimCDFS.
The most expencive but not a winner in any category is to get hold of the USB controller subway and use a USB CDrom but as other's here already pointed out it lack in speed and is as said the most expencive way.
