There are some on Ebay now for about $6 - $8 total. $3.95 + $1.50 shipping and $1.92 + $6 shipping. The former is new, the latter is used.

http://cgi.ebay.com/ONE-TI-TMS4461-TMS4461-15NL-RAM-IC-BOX-64-/370267157659?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item5635a4749b

http://cgi.ebay.com/TMS4461-12NL-TI-256K-Video-RAM-MB81461-HM53461-53461-IC-/370290762883?cmd=ViewItem&pt=LH_DefaultDomain_0&hash=item56370ca483