Is Oracle Wallet available for use with Oracle XE 11gR1
According to the Oracle Database Licensing Information 11g Release 2 document

Oracle Wallet
An Oracle Wallet is a PKCS#12 container used to store
authentication and encryption keys. The Oracle database secure
external password store feature stores passwords in an Oracle Wallet
for password-based authentication to the Oracle database. The Oracle
Wallet may also be used to store credentials for PKI authentication to
the Oracle Database, configuration of network encryption (SSL/TLS),
and Oracle Advanced Security transparent data encryption (TDE) master
encryption keys. Strong authentication services (Kerberos, PKI, and
RADIUS) and network encryption (native network encryption and SSL/TLS)
are no longer part of Oracle Advanced Security and are available in
all licensed editions of all supported releases of the Oracle
database.

That last bit about strong authentication services and network encryption being available in all licensed and supported releases of the Oracle database would suggest that it might be.  It just a matter how licensed and supported are defined.  XE is licensed, but it's support is via Oracle's free discussion forum rather than via the paid for My Oracle Support site