Welcome to the forums!
There are many 16bit pcmcia sound cards, just follow the link in my signature.
The Exp Soundnote only does Adlib FM in DOS, no digital sound.
You can play Doom with the pc speaker for beeps and boops though...
Ebay and Yahoo auctions are the usual sources for old pcmcia cards, and depending where you are located. classified ads might also be an option, like craigslist, something like that.

As for Creative Labs, the only 16bit pcmcia cards they made were modems.

Thanks for the information!

I found that the PC Speaker sound is garbage. I next found out about the OPT3LPT parallel port clone sound card! Yes, it works for music, but not for Doom's sound effects.

I then found the Sound Blaster Audigy 2 ZS Notebook (which is PCMCIA). People are saying that is the best mobile sound card for Windows 98. Also, another post on this forum claims that it can work with DOS: Sound Blaster Audigy 2 ZS Windows 98 Driver or http://mpxplay.sourceforge.net/
Also, my 105CS Toshiba laptop is Windows 95 and Windows 98 compatible as well...

The PCMCIA Sound Blaster Audigy 2 ZS does NOT work with DOS. The PCI card will word with DOS though... although the Creative Labs PCI cards' DOS support is not all that great.

The Audigy 2 ZS Notebook doesn't work in Windows 98 either.

There are only 2 cards that will give you digital sound in pure DOS and not in all games.
They're both really hard to come by, other pcmcia cards will give you adlib/fm music, or General Midi through either an OPL4 chip or Roland Sound Canvas in DOS and digital sound in Windows 9x, but only a very few cards will have SB emulation in Windows.

Though if you play Doom using WinDoom, you'll get digital sound, or you can learn to love the pc speaker sound...