Rockauto.com has them, here is the listing copied from thier catalog
1998 JEEP CHEROKEE 4.0L 242cid L6 MFI (S) OHV : Transmission-Automatic : Control Solenoid Wiki Price
STANDARD MOTOR PRODUCTS Part # TCS48 Auto Trans; 1st & 2nd Gear Solenoid w/ A.T.
* Non-stock item--shipping delayed up to 2 business days $167.79
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AIRTEX / WELLS Part # 2N1191 {#4797403, 5016121AA, TCS64}
Automatic trans.; 4 speed trans.; (3rd Gear Solenoid)
* Non-stock item--shipping delayed up to 2 business days $189.79
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AIRTEX / WELLS Part # 2N1192 {#4797402, 5016120AA, TCS65}
Automatic trans.; 4 speed trans.; (1st & 2nd Gear Solenoid)
* Non-stock item--shipping delayed up to 2 business days $193.79
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Not sure if they're the cheapest, but there are some part numbers to start searching with praetorian.