no, slockets for Slot A dont' exist (Abit has stated that they are technically possible, but economically impractical). You can put Slot A Thunderbirds in, however, they aren't guaranteed to work. The reasoning is that the timing requirements for Thunderbirds and Athlon Classics are different, and the KX133 (the chipset on your KA7 100) is made for Classics, and does not officially support the newer thunderbirds.
The new thunderbirds are getting rarer and rarer to find in Slot form, as only a limted quantity were manufactured. The reason for that is that AMD made them ONLY for the big OEM's who still had AMD 750 chipset based motherboards, which are fully Thunderbird compliant.
Even if a thunderbird does work in your KA7 (a slot A thunderbird), many people have had difficulty overclocking them much over about 800mhz, due to the timing issue.